South Wales - Ecology/Greater West Programme

South Wales - Ecology/Greater West Programme

Project Scope and Delivery

The Greater West Programme (GWP) involved electrifying the route from London to South Wales, via Cardiff, Bristol and the Severn Tunnel. SYSTRA were commissioned to produce the Power and OLE design for various key sections of line from Approved in Principal (AiP) through to detailed design (including feasibility studies). The GWP project proposed various engineering interventions including installation of OLE along the entire route in addition to bridge, tunnel, station and embankment engineering interventions. SYSTRA were commissioned to design 1,800no. foundations in differing ground conditions and constrained locations.

SYSTRA’s Approach

Using traditional pile analysis techniques would result in long sets of twin piles. This would require driving into the ground for a large portion of the route due to the poor ground conditions and deep bedrock in the area. This would have meant large and deep steel piled foundations were proposed. The Environment, Ecology and Sustainability team worked with the Geotechnical team who developed and presented to Network Rail and the Contractor the ‘floating pile’ technique. to identify alternate solutions and then calculate the carbon saving these solutions would have:

  • Reduction in the thickness of steel used in the OLE masts from 16mm to 12mm – this has saved the project 460 tonnes CO2e.
  • Optimisation of foundation depths to reduce the length of piles required by up to 10% - this has saved 2,350 tonnes CO2e.
  • Field drains and ordinary watercourses associated with the Gwent Levels SSSI which crossed or ran adjacent to the railway many of which had water voles and otters within them
  • Badger setts and locations where Japanese knotweed was present
  • Impacts to bats at overbridges
  • Works taking place in urban areas in close proximity to residential and commercial receptors

Managing Environmental Impacts

The EES team were proactive to identify and assess these environmental and ecological risks which were mapped onto GIS software. This allowed the OLE, Geotechnical and Civils design teams to reference the GIS layers into design drawings to them to quickly identify where the constraints were located in relation to their proposed works and, (where required), move engineering elements to avoid or reduce impacts and consent requirements. Through this process, an OLE mast was located away from badger setts and watercourses, avoiding using concrete pad or augured pile foundations in areas in or near Japanese knotweed and reduce impacts to bats through OLE dropper design changes at overbridges.

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